This invention relates to a method for producing an aromatic compound/styrenic compound adduct such as diarylalkane through the reaction of aromatic compound with styrenic compound in the presence of an acid catalyst.
The method for producing an aromatic compound/styrenic compound adduct such as diarylalkane through the reaction of aromatic compound with styrenic compound in the presence of a solid acid catalyst, is proposed in U.S. Pat. No. 4,144,279; Japanese Laid-Open Patent Publication No. S55-24145 and U.S. Pat. No. 4,289,918. The obtained aromatic compound/styrenic compound adduct such as diarylalkane is widely used as insulating oils or several kinds of industrial solvents such as for carbonless copy paper.
For example, in the reaction in which styrene is added to xylene to produce styrenated xylene, the double bond of styrene is lost by the addition to aromatic ring. Accordingly, the styrenated xylene in itself is generally a saturated compound. However, depending upon the kind of used catalyst, the combination of reactants and reaction conditions, unsaturated hydrocarbons such as styrene oligomers of dimer to tetramer are formed by side reaction. Because boiling points of them are close, these compounds are often mixed into the obtained styrenated xylene.
When the thus obtained styrenated xylene is used as a solvent for various purposes, it is apprehended that thermal stability and oxidation resistance of the solvent are impaired due to unsaturated hydrocarbons that are get mixed into the solvent. So that, it is desirable that the contamination of unsaturated hydrocarbons must be avoided as less as possible.
For example, in Japanese Patent Publication No. H6-35399 (Japanese Laid-Open Patent Publication No. S62-42938), there is proposed a method for reducing content of unsaturated double bonds by hydrogenating selectively the formed dimer to tetramer of styrene having unsaturated double bonds, when diarylethane is produced by adding styrene to alkylbenzene in the presence of cation exchange resin catalyst.
When styrenic compound is added to an aromatic compound, it is considered to reduce the proportion of styrenic compound relative to the of aromatic compound in raw material, as one method to suppress the formation of unsaturated hydrocarbons. However, when the concentration of styrenic compound in raw material is reduced, the productivity for intended product is lowered, which is undesirable in view of industrial production.
Meanwhile, as proposed in the foregoing Japanese Patent Publication No. H6-35399, in order to adopt hydrogenation as post-treatment, investment of several equipment for the hydrogenation is necessary, such as a high-pressure reactor for hydrogenation, hydrogen separator, hydrogen compressor for the reuse of unreacted hydrogen and so forth. In addition, it is also disadvantageous in view of the cost for operation.
Accordingly, such a production method is desired that the yield of aromatic compound/styrenic compound adduct can be improved, the contents of unsaturated components can be reduced and in addition, the operation can be done without difficulty at a low cost.